- nanny: enabled nanny use for hotplugging (bnc#880515)
  To disable again in case of trouble, edit /etc/wicked/common.xml
  and set <use-nanny>false</use-nanny>, restart wickedd.service
  and execute "wicked ifup all" to start the interfaces directly.
- ifdown: flush addrs and routes on device-down (bnc#885236)
- dhcp6: do not break ifdown if release fails (bnc#884012)
  When the interface is not ready to send out a lease release,
  commit the lease drop and notify wickedd, so ifdown goes on.
- ifup: update client-info and client-state on device-ready,
  do not detect persistance but set if requested only (bnc#876845).